1. Field of the Invention
The present invention is in the field of apparatus for applying a sizing composition to at least one side of a traveling web. In the preferred form of the invention, a continuous system is provided whereby a sizing composition is constantly being delivered to liquid ponds formed at the nip, and a vacuum is used to control the depth of the ponds to a sufficiently small value to facilitate high speed operation. Sizing composition withdrawn by means of the vacuum is recirculated to a reservoir from which it is fed into the ponds as required.
2. Description of the Prior Art
Sizing operations of the past have usually made use of a pond of liquid material consisting of a sizing or coating solution of a wide range of viscosities at the nip of a pair of oppositely rotating rolls. The paper web was directed through the coating nip for simultaneous application of the sizing composition onto both surfaces of the web.
Experience has shown that controlling the depth of the pond of sizing material at the nip is important in high speed application to control splashing and pond turbulence. If the pond becomes too thick, the entire operation must be slowed down. Furthermore, the inability to control pond depth precisely tends to provide an uneven flow of sizing agent along the cross machine direction of the paper thereby leading to a non-uniform application of the sizing.